JPH08271439A - Inspection equipment and production of exposing system or device employing it - Google Patents

Abstract

PURPOSE: To inspect the surface conditions conveniently and accurately by acquiring image information of a surface to be inspected using an image sensor in an optical system and passing the signal through an electrical low band cut filter. CONSTITUTION: A laser beam 6 emitted from a semiconductor laser 4 is converted through a collimator lens 5 into a parallel light and a linear illumination area on the pellicle face 2 of inspection surface is irradiated with a parallel beam 6. When a foreign matter 20 is present on the illumination area, scattering light is generated substantially isotropically and focused in the vicinity of a one-dimensional image sensor 8 through a distributed refractive index microlens array 7. Signals from the sensor 8 are converted at an analog preprocessing section 9 into time series signals and fed to a low band cut filter 10. Noise output of pellicle frame signal is lowered by taking advantage of the difference in frequency band between the foreign matter signal from the filter and the noise signal of scattering light from the pellicle frame but the level of foreign matter signal is not lowered. Magnitude of the foreign matter 20 is identified at a signal processing section 11 based on the signal from the filter 10 and the position is operated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection apparatus, for example, a surface state inspection apparatus for detecting foreign substances attached to a reticle or a photomask used in a semiconductor manufacturing apparatus.

[0002]

2. Description of the Related Art In a process of manufacturing a semiconductor device such as an IC, a circuit pattern for exposure formed on a substrate such as a reticle or a photomask is coated with a resist by a semiconductor printing apparatus (stepper or mask aligner). It is manufactured by transferring it onto the wafer surface.

At this time, if a foreign matter such as a pattern defect or dust exists on the surface of the substrate, the foreign matter is transferred together with the original pattern, which causes a decrease in the yield of IC manufacturing. Especially when a reticle is used and a circuit pattern is repeatedly printed on the wafer surface by the step-and-repeat method, if one harmful foreign substance is present on the reticle surface, the shadow of the foreign substance is printed on the entire surface of the wafer. As a result, the yield of the IC manufacturing process is greatly reduced.

Therefore, it is indispensable to detect and remove the presence of foreign matter on the substrate in the IC manufacturing process, and various inspection methods have been conventionally proposed. In general, a method of utilizing the property that foreign matter isotropically scatters light is often used.

Reticles and photomasks are roughly inspected by a method of inspecting a patterned substrate surface (pattern surface) (a pattern surface inspection method), a blank surface on the back surface of which there is no pattern, or a dust-proof substrate. It is divided into a method for inspecting the pellicle surface (blank surface inspection method).

For example, as a method for inspecting foreign matter on a pellicle surface or a blank surface, a certain area on the inspection surface is irradiated with inspection light all at once, and scattered light from the foreign matter is first-ordered by a gradient index microlens array or the like. An inspection apparatus has been proposed which forms an image on the original line sensor or defocuses it and inspects it based on the output of the line sensor.

[0007]

However, since the diffusely reflected light from the pellicle frame is much larger than the scattered light from the foreign matter, the noise output due to the scattered light from the pellicle frame detected by the line sensor is also high, and the pellicle The pedestal rises near the frame (see Fig. 9).

That is, in the vicinity of the pellicle frame, the swelling output of the pedestal is added to the scattered light signal from the pure foreign matter, which makes it difficult to accurately detect the size of the foreign matter. This means that the inspectable area of the inspection surface becomes narrow.

The present invention is to solve the problems of the above-mentioned conventional techniques, and to provide an inspection apparatus which can inspect the surface state of the inspection surface simply and with high accuracy, and further, this inspection apparatus. It is intended to provide an exposure apparatus and a device manufacturing method using the.

[0010]

An inspection apparatus of the present invention for solving the above-mentioned problems is an optical system including an image sensor for taking in image information of an inspection surface, and an electric low band cut filter for a signal from the image sensor. And a filter means for applying.

Here, the inspection surface is, for example, a reticle.
The optical system has, for example, a gradient index microlens array or a rotationally symmetric lens.

Further, the exposure apparatus of the present invention is characterized by having means for inspecting a substrate using the above inspection apparatus and means for performing an exposure transfer process using the inspected substrate. Is.

Further, the device production method of the present invention is characterized by producing a device using the exposure apparatus.

[0014]

[Embodiment 1] FIG. 1 is a configuration diagram of a first embodiment of the present invention.

A laser beam having a divergence angle emitted from the semiconductor laser 4 is converted into parallel light by a collimator lens 5. The collimated laser beam 6 irradiates the pellicle surface 2, which is the inspection surface, with a linear illumination area at once.

When the foreign matter 20 exists on the laser beam illumination area, scattered light is almost isotropically generated by the foreign matter. The scattered light is imaged in the vicinity of the one-dimensional image sensor 8 by a gradient index microlens array (hereinafter referred to as “lens array”) 7 arranged along the laser beam illumination area.

In the case where the sensor surface of the one-dimensional image sensor 8 has a dead zone, the dead zone eliminates the oversight of foreign matter. Therefore, the relationship between the distance between the lens array 7 and the one-dimensional image sensor 8 is as shown in FIG. , The front focal length of the lens array (distance from the inspection surface to the lens array)
And the rear focal length (distance from the lens array to the sensor surface) is kept the same so that the lens array 7 is defocused to some extent from the original best image forming position.

The signal from the one-dimensional image sensor 8 is converted into a time-series signal by the analog preprocessing unit 9 and then introduced into the low band cut filter 10. As will be described later, the low-band component cut filter 10 sufficiently reduces the noise output of the pellicle frame signal by utilizing the difference in the signal frequency band between the foreign object signal and the noise signal due to the scattered light of the pellicle frame, and the foreign object signal. Is set to a frequency band that does not reduce

Based on the signal from the low band component cut filter 10, the signal processing unit 11 calculates the size (ranking) of the foreign matter and the foreign matter existing position according to the signal strength.

In the above detection operation, a stage mechanism (not shown) is used to move the entire optical system 12 in a direction perpendicular to the longitudinal direction of the image sensor 8 (perpendicular to the paper surface) relative to the reticle. The entire reticle is inspected by moving it linearly.

Next, details of the signal processing of this embodiment will be described.

The signal from the one-dimensional image sensor is shown in FIG.
As shown in (a), it is obtained as an output for each pixel.
In FIG. 3A, the signal width of the foreign matter signal on the sensor is 6 to 7 pixels (300 to 400 μm), whereas the pellicle frame signal is an excessive signal and its signal width is 26 to 30 pixels. (1500 to 1800 μm).

A signal from the one-dimensional image sensor is converted into a time-series signal as shown in FIG. 3 (b) when the analog preprocessing unit 9 is driven by a clock of 2 Mhz per pixel, for example. In FIG. 3B, the signal width of the foreign matter signal is about 300 Khz, while the spread width of the pellicle frame signal is about 70 Khz, which is different in the frequency band. By utilizing this, if the cutoff frequency of the low band cut filter is set to about 200 Khz, the intensity of the foreign matter signal is not reduced and the noise signal due to the unnecessary pellicle frame can be reduced. The graph of FIG. 4 shows the frequency characteristics of the low band cut filter used in this embodiment.

The graph of FIG. 2 shows the state of signal output after passing through the low band component cut filter as shown in FIG. It can be seen that the rise of the pedestal in the vicinity of the pellicle frame entering the inspection area is reduced by the action of the low band component cut filter, as compared with the conventional one shown in FIG. Therefore, it is possible to detect the foreign matter in the central portion of the inspection area and in the vicinity of the pellicle frame with the same high accuracy.

In this embodiment, the configuration example in which the light is defocused on the sensor surface has been described. However, even in the configuration in which the light is focused on the sensor surface, the aberration and the like of the condensing optical system are As a result, the circle of least confusion may spread, so it is effective to provide a low-band cut filter.

Further, as another function and effect of the present embodiment, by providing the low band cut filter, it is easy to discriminate between the continuous circuit pattern noise and the specific pulse foreign matter signal in the inspection of the pattern surface of the reticle. I have to.
That is, since the signal band of the continuous scattered light generated from the circuit pattern having regularity and the signal of the pulsed scattered light from the foreign matter are different, the low frequency cut filter causes It is possible to reduce the noise signal and improve the detected S / N ratio of the foreign matter signal.

As described above, the low frequency cut filter can effectively remove the unnecessary light from the pellicle frame, the circuit pattern, etc., and the foreign matter inspection can be performed at a high S / N ratio.

<Embodiment 2> FIG. 5 shows the configuration of the second embodiment. In the figure, the same reference numerals as in FIG. 1 above denote the same members. In the figure, 17 is a rotationally symmetric lens, and 18 is a one-dimensional image sensor.

In the first embodiment, the case where the microlens array is used as the scattered light converging means and the inspection area is seen at the same magnification has been described, but in the present embodiment, a general rotationally symmetric lens 17 is used to reduce the size. It is an optical system. This embodiment also has the same effect as the first embodiment.

<Third Embodiment> FIG. 6 shows the structure of a third embodiment. In the figure, the same reference numerals as in FIG. 1 above denote the same members. In the figure, 26 is a light source such as a lamp, and 28 is a two-dimensional image sensor.

In the first and second embodiments, a one-dimensional image sensor is used and the entire surface of the substrate is inspected by moving the inspection substrate and the optical system relatively. In this embodiment, the image sensor is two-dimensional. An image sensor is used to receive light all at once. This embodiment also has the same effect as the first embodiment.

<Embodiment 4> FIG. 7 is a view showing an embodiment of a manufacturing system for manufacturing a semiconductor device by printing a circuit pattern of an original plate such as a reticle or a photomask on a silicon wafer. The system roughly includes an exposure device, an original storage device, an original inspection device, and a controller, which are arranged in a clean room.

Numeral 901 is a far-ultraviolet light source such as an excimer laser, numeral 902 is an illumination system unit, and the exposure position E.I. P. It has the function of illuminating the original set in the above at the same time (batch) from above with a predetermined NA (numerical aperture). Numeral 909 designates a circuit pattern formed on the original plate as a silicon wafer 9
10 is an ultra-high resolution lens system (or mirror system) for transferring onto the wafer 10, and the wafer is moved to the moving stage 9 during printing.
The exposure is repeated while shifting each shot according to the step feed of 11. Reference numeral 900 denotes an alignment optical system for aligning the original and the wafer prior to the exposure operation, and has at least one original observation microscope system. An exposure apparatus is configured by the above members.

On the other hand, reference numeral 914 denotes an original storage device which stores a plurality of originals inside. Reference numeral 913 is an original inspection device, which includes any of the configurations of the above-described respective embodiments. The original inspection device 913 detects that the selected original is pulled out from the original storage device 914 and the exposure position E.E. P. The foreign matter inspection on the original plate is performed before the setting of the foreign matter. The principle and operation of the foreign matter inspection are the same as in any of the above-described embodiments. The controller 918 is for controlling the sequence of the entire system, and controls the operation commands of the original storage device 914 and the original inspection device 913, as well as the basic operations of the exposure apparatus, such as alignment, exposure, and step feed of the wafer. To do.

The production process of a semiconductor device using the system of this embodiment will be described below. First, the original storage device 914
The original to be used is taken out and set in the original inspection device 913. Next, the original inspection device 913 inspects the foreign matter on the original. As a result of the inspection, when it is confirmed that there is no foreign matter, this original plate is exposed at the exposure position E. P. Set to.
Next, the silicon wafer 910 which is the exposure target is set on the moving stage 911. Then, according to the step-and-repeat method, the original pattern is reduced and projected onto each region of the silicon wafer while shifting each shot according to the step feed of the moving stage 911, and exposure is repeated. After the exposure on one silicon wafer is completed, the silicon wafer is accommodated and a new silicon wafer is supplied, and similarly, the exposure of the original pattern is repeated by the step & repeat method. The exposed silicon wafer that has been exposed is subjected to processing such as development and etching by an apparatus provided separately from this system. Then, a semiconductor device is manufactured through an assembly process such as dicing, wire bonding, packaging and the like. According to this embodiment, it is possible to produce a highly integrated semiconductor device having a very fine circuit pattern, which has been difficult to produce conventionally.

<Embodiment 5> FIG. 8 is a diagram showing an embodiment of an original plate cleaning inspection system for manufacturing a semiconductor device. The system is roughly: original storage device, cleaning device,
It has a drying device, an inspection device, and a controller, which are arranged in a clean chamber.

Reference numeral 920 denotes an original storage device which stores a plurality of originals and supplies the originals to be cleaned. A cleaning device 921 cleans the original plate with pure water. 92
A drying device 2 dries the washed original plate. 9
Reference numeral 23 denotes an original plate inspection apparatus, which includes the configuration of any one of the previous embodiments, and inspects foreign substances on the original plate that has been cleaned using any of the methods of the above-described embodiments. A controller 924 controls the sequence of the entire system.

The operation will be described below. First, the original plate to be cleaned is taken out from the original plate storage device 920 and supplied to the cleaning device 921. The original plate cleaned by the cleaning device 921 is sent to the drying device 922 to be dried. After the drying, it is sent to the inspection device 923, and the inspection device 923 inspects the foreign matter on the original plate by using any one of the methods of the previous embodiments. If no foreign matter is found as a result of the inspection,
The original is returned to the original storage device 920. When a foreign substance is confirmed, the original is returned to the cleaning device 921 to perform a cleaning / drying operation and then an inspection is performed again, and this is repeated until the foreign substance is completely removed. Then, the completely cleaned original plate is returned to the original plate storage device 920.

Thereafter, the cleaned original plate is set in an exposure apparatus, and a circuit pattern of the original plate is printed on a silicon wafer to manufacture a semiconductor device. As a result, it is possible to manufacture a highly integrated semiconductor device having a very fine circuit pattern, which has been difficult to manufacture in the past.

[0040]

As described above, according to the present invention, it is possible to effectively suppress the influence of unnecessary light, and it is possible to perform highly accurate foreign matter inspection in a wide area of the inspection surface. Particularly, it exhibits an excellent effect in the inspection of a reticle having a pellicle frame.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a state of a signal from a one-dimensional image sensor.

FIG. 3 is a diagram showing how a signal is output.

FIG. 4 is a diagram showing an example of frequency characteristics of a low band cut filter.

FIG. 5 is a configuration diagram of an apparatus according to a second embodiment.

FIG. 6 is a configuration diagram of an apparatus according to a third embodiment.

FIG. 7 is a configuration diagram of an embodiment of an exposure apparatus having an inspection apparatus.

FIG. 8 is a configuration diagram of an embodiment of a cleaning device having an inspection device.

FIG. 9 is a diagram showing a state of a signal from a one-dimensional image sensor of a conventional device.

[Explanation of symbols]

1 reticle 2 pellicle 3 pellicle frame 4 laser diode 5 collimator lens 6 laser beam 7 lens array 8 one-dimensional image sensor 9 analog pre-processing unit 10 low-band cut filter 11 signal processing unit 20 foreign matter P ₁ , P ₂ foreign matter signal

Claims (9)

[Claims] 1. An inspection apparatus comprising: an optical system including an image sensor for taking in image information of an inspection surface; and a filter means for applying an electric low band cut filter to a signal from the image sensor. 2. The inspection apparatus according to claim 1, wherein the inspection surface is a reticle surface or a pellicle surface. 3. The inspection apparatus according to claim 1, wherein the optical system has a gradient index microlens array. 4. The inspection apparatus according to claim 1, wherein the optical system has a rotationally symmetric lens. 5. The inspection apparatus according to claim 1, wherein the image sensor is a two-dimensional image sensor. 6. The image sensor is a one-dimensional line sensor, and has means for moving the optical system relative to an inspection surface in a direction perpendicular to the longitudinal direction of the one-dimensional line sensor. The inspection device described. 7. The inspection apparatus according to claim 1, wherein the optical system defocuses the image of the inspection surface onto the image sensor to form an image. 8. A means for inspecting a substrate by using the inspection apparatus according to claim 1, and a means for performing an exposure transfer process by using the inspected substrate. Exposure equipment. 9. A device production method, wherein a device is produced by using the exposure apparatus according to claim 8.